A new P,S-coordinating ferrocenyl ligand: synthesis of a precursor and its coordination compounds with Pd^II and Pt^II

Abstract

In our ongoing development of ferrocene ligands, 1-dimethylamino-2-(diphenylphosphinothioyl)ferrocene is being used as a convenient building block to obtain racemic or enantiomerically pure ligands. Using this building block in large excess allowed the formation of several by-products, two of which have already been reported; the structure of a third by-product, namely 1-(diphenylphosphinothioyl)-2-{[(diphenylphosphinothioyl)sulfanyl]methyl}ferrocene, [Fe(C5H5)(C30H25P2S3)], is presented here. The crystal structure is built up from a ferrocene unit, with one of the cyclopentadienyl (Cp) rings substituted in the 1- and 2-positions by a protected diphenylphosphinothioyl group and a [(diphenylphosphinothioyl)sulfanyl]methyl fragment, -CH2SP(=S)Ph2. There are C-H...S interactions which result in the formation of chains parallel to the c axis. After desulfurization, the crude material was then reacted with Pd and Pt (M) precursors [MCl2(CH3CN)2] to yield two isostructural dinuclear complexes arranged around twofold axes, namely (R,R/S,S)-bis{μ-[2-(diphenylphosphanyl)ferrocen-1-yl]methanethiolato-κ(3)P,S:S}bis[chloridopalladium(II)] pentane disolvate, [Pd2{Fe(C5H5)(C18H15PS)}2Cl2]·2C5H12, and the platinum(II) analogue, (R,R/S,S)-bis{μ-[2-(diphenylphosphanyl)ferrocen-1-yl]methanethiolato-κ(3)P,S:S}bis[chloridoplatinum(II)] toluene monosolvate, [Pt2{Fe(C5H5)(C18H15PS)}2Cl2]·C7H8, in which the two metal atoms present a slightly distorted square-planar geometry formed by two bridging S atoms and P and Cl atoms. The P,S-chelating ligand results from the rupture of one of the P-S bonds in the starting ligand. These dinuclear complexes display a butterfly geometry. Surprisingly, only the (R,R/S,S) diastereoisomer has been isolated.